I'm glad you are getting a second opinion I'm not sure if your Onc is up to date on cancer either.
I had a lumpectomy the first time also and it was stage II. Second time the Onc told me that she does a mastectomy when it's the second time around. I had to decide if I wanted both breast removed which the Onc highly recommended and I did.
There was a lady on this site that her Onc had told her basically the same thing(she was a nurse) so she went to a breast cancer center in Pennsylvania and she's doing great.
Let me know what the Onc says about the MRI. Prayers & Hugs Ruby